In typical storage phosphor imaging systems, a storage phosphor media is exposed to an image-wise pattern of short wavelength radiation to record a latent image. Typically, X-ray radiation is employed to record the latent image. The latent image is read by impinging, onto the media, radiation having a wavelength approximating the stimulation wavelength of phosphor. Upon stimulation, the storage phosphor emits radiation that typically has a wavelength different from the stimulation wavelength. Usually, the wavelength of the stimulating radiation does not overlap with the wavelength of the emitted radiation. For example, stimulating radiation typically has a relatively long wavelength such as red or infrared light. The emitted radiation, on the other hand, is usually of a shorter wavelength, such as blue or violet light. To produce a signal useful for electronic image processing, the storage phosphor is scanned in a raster pattern by a laser, causing the phosphor to emit radiation. The intensity of the emitted radiation is proportional to the quantity of short wavelength radiation used to record the latent image. The emitted radiation from the storage phosphor is collected and sensed by a photo-detector, such as a photomultiplier tube, to produce electronic image signals corresponding to the intensity of the emitted radiation sensed.
To optimize the signal-to-noise ratio, it is desirable to collect as much of the emitted light as possible and to direct it to the photo-detector. Many prior art light collection and detection systems have been provided. U.S. Pat. No. 5,369,481 to Berg et al. discloses a spectrometer including an integrating sphere having an interior surface coated with a highly reflective material. Light from an incandescent lamp is diffused within the sphere prior to reaching a sample. The coating is preferably spectrally flat, but may be color-correcting absorbing material to reduce red and green color elements in the light. A set of three detectors measure the total light reflected from the sample. The detector senses light reflected from various surfaces, dependent upon the spatial position of the detector in the sphere. The light sensed includes specularly reflected light, the source light diffusely reflected by the sphere, and the light reflected from the sample minus the specular component. Each detector includes a set of wavelength discriminating filters to pass only one selected wavelength for measurement at a time.
U.S. Pat. No. 5,274,228 to Kaplan discloses a light collector for a film scanner comprising an integrating light conducting cylindrical rod with a coating of diffusely reflective paint. The film is scanned with a laser light beam. Light entering a slit in the cylinder is directed to a photo-detector. The coating material is a high reflectivity spectrally broad white paint and the rod itself is transparent glass which is not colored.
U.S. Pat. No. 5,140,160 to Boutet et al. discloses a collector for storage phosphor imaging systems including a planar mirror and side-by-side pyramidal mirror which collect light and direct it to a photo-detector positioned at a centrally located aperture in the planar mirror. A drawback with the prior art collection/detection systems is that portions of stimulating radiation of a scanning beam may reflect from a sample surface and strike the surfaces of the collector, causing the reflected catoptric stimulated radiation to impinge upon the sample in an area other than where the scanning beam is focused, providing a false indication of signal strength.
What is needed is a collection/detection system that prevents catoptric stimulating radiation from impinging upon a phosphor storage sample being read by a scanning beam.